Interruption of blood flow to the kidney for one hour or more causes a reduction in the rates of renal metabolism and renal function following reinstatement of the circulation. The response to ischemia may be brought on by changes of the tissue occurring during that period of time when blood flow in interrupted and/or during the post-ischemic period when the magnitude of GFR and total renal blood flow is below control valves. The experiments in this proposal are designed to assess the role of each of the periods in inducing change to the tissue which can effectuate the observed response to ischemia. Experiments are also designed to evaluate the functional importance of the renal collateral circulation during a time when flow through the renal artery is stopped. The sensitivity of aerobic metabolism, transport and synthetic processes of both cortex and medulla will be evaluated as they are changed by ischemia. The interrelationships between function and metabolism will be evaluated in terms of both the duration and type of ischemia induced. Likewise, the mechanism by which ischemic conditions bring about the observed response will be sought.